Positive displacement hydraulic diaphragm type pumps are known in the art for delivery of a pumped process fluid by a means of a pumping action between inlet and outlet valves. Hydraulic diaphragm type pumps typically make use of a deformable diaphragm fluidly connected to a hydraulic fluid chamber and located between the inlet and outlet valves between which the process fluid is pumped by constrictive pressure exerted by the diaphragm. The diaphragm is in turn forced to move by a powered hydraulic fluid displacement mechanism that displaces hydraulic fluid into and out of the hydraulic fluid chamber surrounding the hydraulic diaphragm. One particular type of diaphragm is the hose diaphragm.
A deformable hose diaphragm is typically a generally cylindrical membrane, or bladder, with 2 openings, one at substantially each end of the hose diaphragm, to separate the process fluid inside of the diaphragm from a hydraulic fluid chamber surrounding the diaphragm. The hose diaphragm is typically constructed from substantially impervious materials permissive of deformation to change the internal volume of the diaphragm, such as pliable and/or elastic materials like polymeric, plastic, metallic foil, rubber materials, in solid or laminated form, for example. Preferably the process fluid flows from one end through to the other end of the hose diaphragm. Due to the substantially straight flow of the process fluid through the hose diaphragm, and the separation between the process fluid and the hydraulic fluid, this type of positive displacement pump is typically suited for pumping highly viscous materials, abrasive, reactive or corrosive materials, slurries and sludges, as well as less viscous fluids at a wide range of pressures. Although hose diaphragm pumps are discussed in particular below, the field of the present invention applies to all forms of hydraulic diaphragm pumps. In the case of hydraulic diaphragm pumps using an alternate diaphragm such as a flat or substantially planar diaphragm, separately or in combination with a hose diaphragm, the description below may be interpreted such that the two working surfaces of the alternate diaphragm correspond to the inside and outside of a hose diaphragm.
Hydraulic diaphragm pumps according to the art may typically provide a constrictive pressure around the diaphragm to provide the necessary pumping action of the process fluid inside the diaphragm by displacing the hydraulic fluid in a hydraulic fluid chamber surrounding the diaphragm, to constrict (effectively decreasing the internal volume of the diaphragm and the process fluid within) and expand (effectively increasing the internal volume of the diaphragm and the process fluid within) the diaphragm respectively. During operation of the hydraulic diaphragm pump, changes in the volume of hydraulic fluid in the hydraulic fluid chamber(s) surrounding the hydraulic diaphragm(s) may result due to leaks or losses of hydraulic fluid such as through seals, connections and/or imperfections in the hydraulic fluid system. Such changes in the volume of hydraulic fluid in the hydraulic fluid chamber(s) of the pump may result in undesired changes to the volume and/or range of extension and constriction of the hydraulic diaphragm, such as excessive expansion or stretching of the diaphragm on the suction portion of the pump stroke. Such changes in the extension/constriction operating range of the diaphragm may lead to undesirable reduced pump efficiency, wear, and/or premature failure of the hydraulic diaphragm.
Accordingly, there is a need for a hydraulic fluid control system for a hydraulic diaphragm pump that addresses some of the limitations of existing hydraulic diaphragm pump designs, and particularly hose diaphragm pump designs according to the art.